Process for the production of erythrina alkaloids



Patented Dec. 10, 1946 PROCESS FOR THE PRODUCTION 0F ERYTHRINA ALKALOIDS Karl Folkers, Plainfield, and Randolph '1. Major, Mountainside, N. J assignors to Merck & 00., Inc., Rahway, N. J a corporation of New Jersey No Drawing. Original application November 13,

1942, Serial No. 465,460. Divided and this application June 3, 1944, Serial No. 538,699

This invention relates to a physiologically active alkaloid, and to processes for its production.

The alkaloid of the present invention exhibits a potent curare-like action, and is particularly useful for the release of spasm and plastic muscular rigidity in patients afllicted with spastic paralysis, and for modification of the severity'of metrazol convulsions, thereby preventing fracture in the convulsive therapy of the psychoses.

Our new alkaloid may be produced from seeds or plant parts of species of Erythrina. When such seeds or plant parts are extracted with water, alcohol, etc., (after removal of fats) a crude extract is obtained, which exhibits high paralysis potency. When an aqueous solution of that fraction is made slightly or weakly'alkaline, and extracted with a solvent immiscible in water, such as chloroform, an active alkaloidal fraction is obtained which has been called the free alkaloidal fraction.

After the free alkaloidal fraction had been produced, is was discovered, surprisingly, that other new alkaloids of different type could also be produced from Erythrina species. We have called these last-named alkaloids the combined alkaloids because they are combined with an acid through an ester linkage. These new combined alkaloids appear to be esters of sulfoacetic acid, HOaSCHzCOzH, and still other new alkaloidal molecules. This is evidenced by the fact that acid or alkaline hydrolysis of the new combined alkaloids yields two fragments in each instance, the sulfoacetic acid and an alkaloidal portion which we have called the liberated alkaloid.

To our knowledge, such"combined alkaloids are without parallel in alkaloid chemistry.

These new alkaloidal esters of sulfoacetic acid also exhibit the physiological action of curare, and likewise possess the valuable property of forming soluble sodium salts, which renders them suitable for injection in that form.

The free fraction maybe produced from seeds or plant parts of the Erythrina species. One process for its production may involve the following general steps described with particular reference to seeds as starting materials:

1. Treatment of the seeds to remove fats;

2. Extraction of the total alkaloids with'a solvent such as methyl or ethyl alcohol;

3. Removal of the solvent, and dissolving of the residue in water;

, 4. Clarification of the aqueou solutionby weakly acidifying and extracting with petroleum ether and then with chloroform, to' remove traces of fats;

3 Claims. (01. 260236) 5. Alkalinization of the clarified aqueous solu tion with a, weak alkalinizingagent;

6. Extraction of the weakly or slightly alkalinized aqueous solution with chloroform, which selectively removes the free alkaloidal fraction and thus separates the free and combined fractions.

Certain variations may be practiced in carrying out the invention. Thus, for example (a) Step 1 may be omitted, and the fats 'removed at Step 4 of the process;

(b) Water may be utilized for extraction Step 2, in which event Step 3 may be omitted.

(c) The alkaloid, hypaphorine, which may also be obtained from species of Erythrina may be produced before producing the physiologically active alkaloids, by acidifying the clarified aqueous solution remaining after'Step 4, concentrating to small volume, and refrigerating, whereupon. a hypaphorine salt crystallizes out. Since the combined alkaloids may be hydrolyzed to liberated alkaloids by acid, the acid treatment for production of the hypaphorine salt should be car'- ried out as rapidly as possible, in order that the free fraction may be produced selectively onfurther working up of the extract as previously described. 7 r

(d) In treating the bark'of roots, stems, or

flowers, the resinous substances may be separated out together with the alkaloidal material, by

extractin such starting materials directly with methy1 alcohol or ethyl alcohol. Ontreatment with 'acidulated water; the resinous substancesare separated from the alkaloidal material, and may be removed by concentration and filtration.

The free alkaloidal fraction obtained according to the above-described procedures may om= prise substantially preponderantly the free in dividual, alkaloidal substance which we have called erythroidine, or may comprise several free individual alkaloids in varying proportions.

In addition to our alkaloidal substance,

erythroidine, we have also produced several 1 other individual free alkaloids which we have called erythraline, erythramine, and erythratine,

respectively. Hereinafter in the specification and claims where the term free fraction is used it is intended to define the chloroform-soluble fraction of Erythrina alkaloids. i

In the case of those Erythrina species, such' as E. americana, E. berteroana, and E. Poeppigiana, for example, where the free fraction comprises substantially preponderantly our erythroidii'i'e, that product is directly obtainedby the process outlined above. Thus the product obtained at Step 6 of the process described, would be erythroidine. It may be recovered directly as the base, or. may be recovered in the form of an acid salt or hydrohalide by dissolvingthe base in an organic solvent such as methyl or. ethyl alcohol, for instance, treating with an agent adapted to produce the desired acid salt or hydroe to subject the fraction to special treatment for the selective production'of any one of the free individual alkaloids. Thus, in the case of a species of Erythrina such as, E. costarz'censzs, for

example, the free alkaloidal fraction obtained therefrom may be treated with strong alkali solution to cause a rupture of the lactone ring in erythroidine, and form the alkali salt of the resuiting acid, thus rendering the alkaloid insoluble in the usual organic solvents. The remaining free alkaloids which comprise the free fraction are unafiected by the treatment with strong alkali and may be recovered by extracting the alkaline solution with a water-immiscible organic solvent, such as chloroform. After production of the unaffected free alkaloids, the lactone ring of-erythroidine may be reformed by acidifying the'alkaline solution, and refluxing, .or by permitting the acidified solution to stand for some time. Upon acidificatiomthe salt or hydrohalide of "erythroidine corresponding to the acidifying agent employed, may be recovered by weakly alkalinizing the solution, as by treatment thereof with, sodiumbicarbonate, and extracting the weakly alkaline solution with a solvent such as chloroform.

I Our "erythroidine is a crystalline material, has the empirical formula. C1cI-I19NO3,.is a lactone .which is susceptible to destruction by strong which he reports thathe obtained in admixture with resinous and other foreign materials. That it is not the alkaloid which we have called .erythroidine is clear, inthelight of the brief discussion of his process given by{ Altamirano. For example, Altamirano states that in order to isolate his alkaloid from the crude extract, he utilized potassium hydroxide. He states that the extract was dissolved'in water, alkalinized with potash solution, mixed with sulfuric ether, and agitated. He reports. that in this way he isolated. 052 gram of a substance, which he describes as follows; Colorless when fresh,but after having been exposed to the action of air for some time, changes to a red color; has a special odor, and a definitely alkaline action soluble in water, giving it a milky appearance, deliquescent, amorphous; did'not form the prismatic crystals of coralloidine alkali, forms a crystalline hydrochloride melting .at around 232 0., usually in the range of 223 232C, and is a mixture of stereoisomers; The

.,term ery'throidine as used hereinafter in the specification and claims is intended to definethis lactone. 4 r

Previously, Altamirano has reported the production of a crude extract from a species of 'Erythrina which he called E. coralloides (Gaceta Medica de Mexico,- vol. 23, No. 18, pp. 369 -92, 1888).. The Altamirano paper does not reveal any characterizing data by which the species of .Erythrina with which he worked can be identified and classified, and it is impossible to determine the plant upon which his reported experiments were'carried out. He reports that he produced a crystalline alkaloid from E. coralloides which he called coralloidine, but that such crystalline alkaloid was not a motor-paralyzing principle. Altamirano also reports his experiments on the mother liquors of his coralloidine extraction,1.but

the experiments are not describedin detail, no

with hydrochloric acid.

Our alkaloid erythroidine is distinguished from the substance describedby Altamirano, nor could our erythroidine be :obtained by the generalized processes described by him; Thus, in aqueous solution ouralkaloid,.ferythroidine, is progressively hydrolyzed in the presence of potassium hydroxide, and, furthermore, it is sparingly soluble vin ether. Also, itforms a crystalline hydrochloride. i g A Altamirano further reports that he mixed colorin powder with slaked lime and that, after further treatment he obtained an impure sulfate of the material he callederythroidine. Our new alkaloid which we called erythroidine is susceptible to destruction by strong alkalies, such as slaked lime. i

In view of the difi'iculty encountered-mat tempting to follow the experimental data given by Altamirano, we have attemptedto produce our alkaloid erythroidine from Erythrina covalloides DC. according to the method which we have found effective for its productionfrom other-Erythrina species. We havebeen unable to obtain our alkaloid erythroidine fromE.

coralloides DC. by such processes. 1

The following example illustrates method'of carrying out the present invention, but it is to of illustration and not of limitation.

be understood that this example is'given byway Example About 677 gms. of finely powdered seedsof'E.

costaricensz's, Niehaus 936.4, were extracted continuously for six hours with petroleum ether. The ether extract was concentrated to dryness, yieldingabout 89.8 gins. of an oily residue. The defatted material was then extracted continue .ously withY methanol for hours. Themethquantities of reagents, temperature conditions, or' I the like, being given. Altamirano states thatfrom the mother liquorsof his coralloidine extraction, he obtained a mixture of substances containing, among others, a small quantity of a mate- .rial which he called erythroidine because it appeared to be different from the substance which he had called coralloidine.

' It is impossible to repeat the experiments of Altamirano, due to the paucity of details given, andthe fact that he has not identified the species of Erythrina with which he worked, .and, there- ,fpre, it is impossible; to identify the substance solution was extracted eve 'times with V "tion's of'petroleum ether, and then extracte' form. :The chloroform was remov'ed-frorn the anolic extract was concentrated dryness in vacuo', and yielded 1017.2 'gmsof dry re" e, The dry residue was dissolvedjinu'fiilfl "in of 7 water, and acidfied 'by the addition of l2m11s; or

concentrated hydrochloric acid; 'Ijhe'; acidiijed t rre times with 25 ml. portions of chloroform t remove residual particles'of fatty materia The remaining clear acid solution was cooled in an ice bath to about 10 C., and then neutralized and made alkaline to pH 8.0 with solid sodium'bicarbonate. The alkalinized material was {extracted-ll times with 25 ml. portions of-chloroextracts, in vacuo; and 2.4 gins; of g-umm' r due were obtained.

The residue comprised a mixture of alkaloids, which were separated as follows:

The gum was dissolved in the minimum amount of alcohol and 125 mls. of 5% aqueous sodium hydroxide was added. The solution was refluxed for one hour, cooled, and extracted times with 25 ml. portions of chloroform. The chloroform extracts were concentrated to dryness. 0.86 gm. of gum was obtained. The remaining aqueous alkaline solution Was acidified to PH 2.3 with concentrated hydrochloric acid, and refluxed for one hour. The solution was cooled, and made alkaline to pH 8.0 with sodium .bicarbonate. The alkaline solution was extracted 10 times with 25 ml. portions of chloroform. 1.13 gms. of erythroidine were obtained, after removal of the solvent in vacuo. It was converted to its hydrochloride.

Modifications may be made in carrying out the present invention without departing from the spirit and scope thereof, and We are to be limited only by the appended claims.

This application is a division of our application Serial No. 465,460, filed November 13, 1942, now Patent No. 2,385,266, which is a continuation-in-part of our application Serial No. 233,412, filed October 5, 1938.

We claim:

1. The process that comprises treating an aqueous solution of the free fraction from species of Erythrina comprising free individual alkaloids with strong alkali, extracting the alkaline solution thus obtained with chloroform, acidifying the aqueous alkaline solution remaining after such extraction, heating to reflux the acidified solution, weakly alkalinizing, extracting the weakly alkaline solution with chloroform, and recovering from the last-mentioned chloroform extract the alkaloidal substance erythroidine, a stereoisomeric mixture of formula C16H19NO3.

2. The process that comprises treating an aqueous solution of the free fraction from species of Erythrina comprising free individual alkaloids with sodium hydroxide, extracting the alkaline solution thus obtained with chloroform, acidifying the aqueous alkaline solution remaining after such extraction, heating to reflux the acidified solution, treating with sodium bicarbonate, extracting the weakly alkaline 'solution thus obtained with chloroform, and recovering from the last-mentioned chloroform extract the alkaloidal substance, erythroidine, a stereoisomeric mixture of formula C16H19NO3.

3. The process that comprises treating an aqueous solution of the free fraction from species of Erythrina comprising free individual alkaloids with strong alkali, extracting the alkaline solution thus obtained with a water-immiscible solvent inert to the material extracted, acidifying the aqueous alkaline solution remaining after such extraction, heating to reflux the acidified solution, weakly alkalinizing, extracting the weakly alkaline solution with a waterimmiscible organic solvent'inert to the material extracted, and recovering from the last-mentioned solvent extract the alkaloidal substance erythroidine, a stereoi'someric mixture of formula C16H19N03.

KARL FOLKERS. RANDOLPH T. MAJOR. 

